1. Field of the Invention
The present invention relates to a ball screw, and more particularly to a support structure for a ball screw.
2. Description of the Prior Art
A motion transmission apparatus used on a machine tool normally comprises a screw and a nut movably disposed on the screw. When the nut moves, the object carried by the nut also moves simultaneously with the nut. To prevent sagging of the screw, when the screw is excessively long, the motion transmission apparatus is usually provided with a supporter to support the screw, so that the nut is able to move along the same center line, preventing wear off, temperature rise, and structural deformation, meanwhile, extending the travel length of the nut.
As shown in FIG. 1, an actuator for a ball screw disclosed in U.S. Pat. No. 5,720,202 essentially comprises a rail 12 disposed beside a screw 11, and three support brackets 13 slidably mounted on the rail 12 and the screw 11. The support brackets 13 are controlled to move in an accelerated or decelerated manner by belts 14, 15 and pulleys 16, 17, 18 and 19. With the pulleys, the support brackets 13 can change moving direction and speed to support the screw 11, and to prevent the screw 11 from deformation. However, the structure of this actuator is too complicated, and the portions of the belts 14, 15 for contacting the pulleys 16, 17, 18 and 19 are likely to wear off, causing fatigue or fracture of the belts 14, 15. Therefore, the actuator has low reliability and high maintenance cost.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.